The phenomenon of echo is based on which property of sound?
A. Interference
B. Diffraction
C. Reflection
D. Refraction
Answer: Option C
Solution (By JKSSB Mock Tests)
Echo is the reflection of sound waves from a rigid surface, returning to the listener after a time delay. For distinct echo, minimum distance to reflector is about 17 m (so time delay > 0.1 s, persistence of hearing). Refraction bends sound in media with varying density; interference combines waves; diffraction bends around obstacles. Memory tip: 'Echo = sound reflection like light in mirror'. This application-based question links wave properties to daily-life phenomena, frequently tested in competitive exams to assess conceptual clarity beyond definitions. Always distinguish echo from reverberation (multiple reflections).
Explanation:
Ohm's law applies to ohmic materials (metals) at constant temperature. Non-ohmic devices (diodes, filaments) have nonlinear V-I characteristics. Memory tip: 'Ohmic = linear V-I graph through origin; temperature must be constant'. Conceptual question testing Ohm's law limitations, frequently examined in competitive exams.
Explanation:
The volume of a sphere is given by V = (4/3)πr³. The formula for relative error in volume is (ΔV/V) = 3 × (Δr/r). Since the percentage error in radius (Δr/r × 100) is 2%, the percentage error in volume will be 3 × 2% = 6%. Constants like 4/3 and π do not contribute to the error.
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